Long-Term Evolution (LTE), which is a next generation mobile broadband network standard defined by Third Generation Partnership Project (3GPP), applies an Orthogonal Frequency Division Multiplexing (OFDM) technology and introduces technologies including Multiple Input Multiple Output (MIMO) and so on, and in the meanwhile, is able to support a bandwidth of 1.25 to 20 MHz, thus greatly improving a peak data rate and system capacity, and supporting a downlink peak rate of 100 Mbit/s and an uplink peak rate of 50 Mbit/s in a bandwidth of 20 MHz. Scheduling and radio resource control efficiency is enhanced by a flat network structure, and a continuing time delay is shortened.
A Multimedia Broadcast Multicast Service (MBMS) has been supported by the Third Generation (3G) mobile communications system, and an Enhanced Multimedia Broadcast Multicast Service (eMBMS) constructed in a fourth generation LTE system is viewed as a service with good application prospect in the industry. A method for implementing the eMBMS includes that an intelligent terminal having a video function receives a digital audio/video service in a broadcast/multicast form through a Physical Downlink Multicast Channel (PMCH), and 3GPP protocol standards have provided perfect solutions for implementation and networking methods of the eMBMS.
With the rapid development of the Internet and the popularization of multifunctional mobile terminals having large screens, a large number of mobile data multimedia services and various high bandwidth multimedia services have emerged, such as video conferences, television broadcasting, videos on demand, advertising, online education, interactive games and so on, which satisfies demands of a plurality of services of mobile users on one hand, and brings a new service increasing point for mobile operators on the other hand. It is required by these mobile data multimedia services that a plurality of users is able to receive the same data simultaneously, thus the mobile data multimedia services have features including large amounts of data, long durations and delay sensitivity and so on compared with a common data service.
The MBMS, which is provided by 3GPP so as to effectively utilize mobile network resources, is a technology for transmitting data from data from a data source to a plurality of target mobile terminals, so as to share resources of networks (including a core network and an access network), thus improving the utilization ratio of the network resources (especially a resource of an air interface). The MBMS defined by 3GPP is able to not only implement multicast and broadcast of a pure text low rate message, but also implement multicast and broadcast of a high speed multimedia service, thus providing various rich videos, audios and multimedia services, which undoubtedly complies with the development trend of mobile data in the future, and providing a better service prospect for 3G development.
A UE receiving the MBMS may be in either of the following two states: one of which is Radio Resource Control (RRC) connected (RRC-CONNECTED) and the other one is RRC idle (RRC_IDLE). It may be judged according to the fact whether the UE is receiving a unicast service, that the UE that is receiving the MBMS is in a connected state or an idle state. When receiving the unicast service, the UE is in the connected state, and the UE in the idle state is not in RRC connection with a network side while the UE in the connected state is in RRC connection with the network side.
If the UE is receiving the MBMS in an original cell (which may be also called as a current cell), after the UE leaves the original cell and resides in a target cell (if the UE is in a connected mode, the UE may be switched from the original cell to reside in the target cell, and if the UE is in an idle state, the UE may reside in the target cell from the original cell through a cell selection/reselection process, and the target cell may be also called as a new cell), the UE will read messages (an MBMS control signaling carried on an MBMS control channel, i.e. a Multicast Control Channel (MCCH), is called an MCCH message) of a Broadcast Control Channel (BCCH) and the MCCH to acquire resource configuration information of the MBMS in the target cell. If the target cell and the original cell belong to the same MBMS over a Single Frequency Network (MBSFN) area, that is, the target cell and the original cell belong to this MBSFN area, the UE may not need to read the resource configuration information of the MBMS after entering the target cell, and may directly use the resource configuration information of the MBMS of the original cell (the current cell) to receive the MBMS in the target cell, and a content of the MBMS is carried on an MBMS channel, i.e. a Multicast Traffic Channel (MTCH), thereby implementing MBMS continuity. Each MBMS is carried on one MTCH, and a content of only one MBMS is also carried on each MTCH. The so-called reading of the MTCH in the present disclosure refers to reading of the MBMS content on the MTCH channel. If the target cell and the original cell belong to different MBSFN areas, the UE needs to read the resource configuration information of the MBMS after entering the target cell. If the MBMS that needs to be received by the UE is not sent in the target cell, the UE fails to read the resource configuration of the MBMS after entering the target cell, thus failing the receive the MBMS.
Receiving states of a UE having an MBMS capability includes that the UE is receiving an MBMS and that the UE is interested in receiving an MBMS. That the UE is interested in receiving the MBMS means that the UE has not received the MBMS, but is prepared to receive the same. At the moment, the UE may monitor an MBMS notification message, and further reads an MCCH message and MBMS data according to the MBMS notification message.
Before section start of an MBMS, a Broadcast-Multicast Service Center (BM-SC) performs service announcement first so as to send brief introduction of the MBMS to a UE, such as an Electric Service Guide (ESG), and the announcement may be sent by the following methods: an MBMS bearer, or an interaction method, e.g. a Hypertext Transfer Protocol (HTTP) or a Picture Transfer Protocol (PTP) push method, such as a Short Message Service (SMS), a Multimedia Messaging Service (MMS), HTTP push and so on. The announcement may last after an MBMS session stops. A content of the ESG is carried on User Service Description (USD), and a user may read the ESG content carried on the USD so as to acquire, in advance, an MBMS Service Area (MBMS SA) represented by {TMGI, MBMS Service Area Identity (SAI) list} on the USD, of each MBMS (an MBMS in the present disclosure may be also called as a service for short, wherein a Temporary Mobile Group Identity (TMGI) corresponds to a certain MBMS, and a MBMS SAI list corresponds an SAI list of the service.
A process in which a user is interested in a certain MBMS and starts to read the service is as follows in the related art.
A UE has in advance known a TMGI/TMGIs corresponding to one or more MBMSs including an MBMS that the UE is interested in and it is provided that the MBMS that the UE is interested in is TMGI1. The UE resides in a certain cell, and if the UE is interested in a certain MBMS (provided that the MBMS that the UE is interested in is TMGI1), then the UE needs to find and initially (start) read TMGI1 through the following steps.
Firstly, a System Information Block (SIB) of the cell, which is carried on a BCCH channel, is read. If the UE is interested in a certain MBMS, the UE needs to read SIB 13 (an SIB numbered 13). Configuration information of one or more MCCHs is carried on SIB 13, and each MCCH corresponds to an MBSFN area. By reading SIB 13, the UE may read: 1) an MBSFN area Identifier (ID) corresponding to each MCCH, 2) a configuration parameter of each MCCH (i.e. radio resources where MCCHs are configured, thus facilitating the UE to further read MCCH messages on the radio resources).
Subsequently, the UE may read each MCCH message above to know whether the MBMS that the UE is interested in is carried on a certain MBSFN area. An MBSFN resource configured by an MBSFN area corresponding to each MCCH message, and scheduling information (the UE may know MBSFN resources on which MBMSs are specifically scheduled) of all MBMSs of the MBSFN area are carried on each MCCH message. Each MBMS corresponds to a unique MTCH. In other words, a content of each MBMS is uniquely carried on an MTCH. Specifically, by reading an MCCH message, the UE may read: 1) radio resources on which all MTCHs of an MBSFN area corresponding to the UE are respectively configured; 2) an MTCH on which the MBMS that the UE is interested in is further scheduled. For example, MBMS TMGI1 that the UE is interested in is configured on a certain MTCH of a certain MBSFN area.
Finally, the UE reads a content on the MTCH (e.g. MTCH1) corresponding to the MBMS that the UE is interested in, and further needs to continue reading an MCCH message corresponding to the service that the UE is interested in. Once resource configuration about the MTCH1 changes on the MCCH message, the UE may continue to read MTCH1 on a new radio resource.
In a word, the UE needs to read SIB 13 (MCCH configuration parameters may be acquired) and read MCCHs (an MTCH on which the service that the UE is interested in is carried may be found) and read the MTCH carrying the MTCH on which the service that the UE is interested in so as to find and initially (start) read TMGI1.
During a mobile process, a UE in an idle state generally enters a target cell by a cell selection or reselection flow, and a UE in a connected state generally enters a target cell by using a cell switching flow. Cell selection or reselection belongs to the mobility of the UE in the idle state, and aims at ensuring that the UE in the idle state resides in an optimal cell. In a wireless network, cell selection or reselection is a necessary process, mainly because of the mobility of a UE and the fluctuation of a wireless network, and resulting fluctuation in signal strength and interference levels.
A UE resides in an original cell, and the cell is in a state of receiving a certain MBMS of interest. When the UE moves from the original cell to a target cell, and resides in the target cell through cell selection/reselection (or a switching flow), according to the fact whether the original cell and the target cell belong to the same MBSFN area, the moving process of the UE may be further divided into Intra-MBSFN area mobility or Inter-MBSFN area mobility of the UE.
After the UE resides in a certain cell of a certain MBSFN area (set as MBSFN1) and is able to read the MBMS that the UE is interested in, the UE moves from the original cell (set as cell 1) to the target cell (set as cell 2). At the moment, the UE will read SIB 13 of the target cell so as to know whether there is a change in an MBSFN area of the target cell compared with that of the original cell, i.e. whether cell 2 belongs to the original MBSFN1, and whether the UE can continue receiving TMGI1.
On the other hand, a certain cell may be covered by a plurality of different MBSFN areas. In other words, the cell is in the coverage of the MBSFNs. For example, cell 1 is in overlapped coverage of {MBSFN1, MBSFN2} while cell 2 is in {MBSFN1, MBSFN3}, as shown in FIG. 1.
At the moment, when a UE moves from cell 1 to cell 2, the UE has intra-MBSFN mobility for MBSFN1 while having inter-MBSFN mobility for other MBSFN areas. If an MBMS which is currently received by the UE and the UE is interested in is carried on MBSFN1, the UE may receive the service on both cell 1 and cell 2. However, if the MBMS which is currently received by the UE and the UE is interested in is carried on MBSFN2, the UE moves from cell 1 to cell 2 and may fail to continue receiving the service on cell 2.
In the related 3GPP art, it is always assumed that MBMSs configured on two adjacent MBSFN areas are different. In other words, only the service continuity (the service continuity in the present disclosure indicates whether the UE is able to receive the same MBMS when moving between two cells) of an UE moving in the same MBSFN area is described in the related art, but the related art fails to research and provide the service continuity for a UE to receive the same service when the UE moves between different MBSFNs, especially a solution for maintaining the service continuity in a case that an MBSFN on a target cell fails to carry the MBSM. When the UE moves to a certain cell that cannot carry the MBMS, a network side usually fails to learn such a condition, thus the network side fails to ensure service continuity, the reception of the MBMS by a user side is interrupted and user experience is reduced.
At present, there is not effective solution yet for the problems in the related art.